In some vehicles, power steering systems are designed to provide hydraulic assist to enable a driver to complete a turn of the vehicle. Some known hydraulic steering systems use a recirculating ball style steering gear or a rack and pinion style steering gear, each of which may not have the capability to perform functions such as park assist, lane keeping, lead and pull compensation, drive alert, active return-to-center, active dampening, or stability control assist. In order to provide such additional performance features, a system such as a hydraulic variable effort steering system is typically required.
Some hydraulic steering systems utilize a power steering pump to provide pressurized hydraulic fluid to the steering gear. However, known systems power the power steering pump with a vehicle engine, which consumes vehicle power and fuel. Additionally, the fluid flow rate of the pump is a direct function of engine speed. For example, engine speed is typically low during a parking maneuver and high during highway driving, which results in low fluid flow rates during parking and high flow rates during highway driving. As such, the hydraulic power steering systems with torque overlay capability may be unable to provide park assist or other performance features.